Technical Abstract: Leaf rust, stem rust, and stripe rust are among the most important diseases of wheat and barley worldwide and are best controlled using genetic resistance. To increase the diversity of rust resistance in wheat and barley, a project was initiated to identify and characterize rust resistance genes from the wild species of Aegilops sharonensis (Sharon goatgrass) and Hordeum vulgare subsp. spontaneum (wild barley), respectively. One hundred and two accessions of Ae. sharonensis from Israel, and 318 Wild Barley Diversity Collection (WBDC) accessions from the Fertile Crescent, Central Asia, North Africa, and the Caucasus region were evaluated for resistance to leaf rust, stem rust, and/or stripe rust. Aegilops sharonensis exhibited a wide range of infection types (ITs) in response to leaf rust, stem rust, and stripe rust. The percentage of resistant accessions in Ae. sharonensis was 58.8-78.4% for leaf rust, 11.8-69.6% for stem rust, and 46.1% for stripe rust, depending on the race used and the plant growth stage. Genetic studies with Ae. sharonensis revealed oligogenic resistance to leaf rust and stem rust. Wild barley also exhibited a wide range of ITs to leaf rust and stem rust; however, the overall frequency of resistance was lower than for Ae. sharonensis. The percentage of resistant accessions in wild barley was 25.8% for leaf rust and 5.7 to 20.1% for stem rust, depending on the race used. Resistance to the new virulent stem rust race TTKS (i.e. Ug99), present in eastern Africa, was found in both Ae. sharonensis (70% of accessions) and wild barley (5 of 20 accessions tested). Association mapping for stem rust resistance was applied in the WBDC using Diversity Arrays Technology (DArT) markers. Using the highly conservative P value threshold of 0.001, 14 and 15 significant marker associations were detected when the number of subpopulations (K value) was set for 10 and 8, respectively. These significant associations were in 9 and 8 unique chromosome bins, respectively. Two significant marker associations were detected for resistance to the wheat stem rust race MCC in the same bin as the rpg4/Rpg5 complex on chromosome 7(5H). The presence of a major stem rust resistance gene in this bin on chromosome 7(5H) was validated in a bi-parental mapping population (WBDC accession Damon x cultivar Harrington) constructed with DArT markers. The results from this study indicate that Ae. sharonensis and wild barley are rich sources of rust resistance genes for cultivated wheat and barley improvement, respectively, and that association mapping may be useful for positioning disease resistance genes in wild barley.